[ https://issues.apache.org/jira/browse/CONFIGURATION-394?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Java Developer updated CONFIGURATION-394:
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Priority: Major (was: Minor)
> Providing BeanDiff(or ConfigurationDiff), BeanBatchUpdateListener, and some merge facility
for Configuration(Specially for HierarchialConfiguration) to implement two-phase-commit-like
protocol to alter entire configuration hierarchy in atomic manner.
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: CONFIGURATION-394
> URL: https://issues.apache.org/jira/browse/CONFIGURATION-394
> Project: Commons Configuration
> Issue Type: Improvement
> Reporter: Java Developer
> Original Estimate: 2016h
> Remaining Estimate: 2016h
>
> Sorry for English and for such a generic summary:
> If you have ever worked with Weblogic AdminConsole(Weblogic 10.3 in my case) you would
find out that it save your changes temporary and finally by clicking "Apply changes" it would
save all changes in configurations. If one of the changes is failed then Weblogic would rollback
all changes of configurations. Something like database transaction.
> The general idea could be that you create a clone of your entire or some parts of your
configuration hierarchy, then change the cloned version, and finally apply back the cloned
version on original version of hierarchy. Here when you ask the original configuration hierarchy
to accept new changes then the original hierarchy would compute the Diff between itself and
cloned version and deliver the changes to all listeners that have registered for configuration
changes. If any of listeners are not agree with new changes then all process of applying configuration
would be rolled back!
> Here in this scenario you need some facility to be added to Apache Commons Config and
also to Apache Commons BeanUtils:
> 1- A BeanDiff class that can compute the difference between two JavaBeans. These JavaBeans
are custom classes that programmers write for application configuration (e.g. CacheConfiguration
class). These custom configuration classes would use the apache common config classes to to
store and retrieve the configuration from any source. It can be extended to have ConfigurationDiff
that would represent the changes between two Configuration(shows which properties are altered)
> 2- Cloning entire hierarchy of configuration, I actually do not know whether currently
Apache Commons Config support this feature.
> 3- The most important part is adding some method to Configuration interface which enables
Configuration interface to accept a whole configuration hierarchy and then apply that hierarchy
to itself. The apply process consist of traversing the hierarchy and visiting each node, then
computing ConfigurationDiff for each node and then notifying the registered listeners of that
node for all updates that node has. If one of listeners reject the update then the process
would call rollback method of listeners.
> 4- Some class like ConfigurationUpdateListener(or BeanUpdateListener) that has some
method like :
> public abstract void prepareUpdate(ConfigurationUpdateEvent updateevent)
> throws ConfigurationUpdateRejectedException;
> public abstract void activateUpdate(ConfigurationUpdateEvent updateevent)
> throws ConfigurationUpdateFailedException;
> public abstract void rollbackUpdate(ConfigurationUpdateEvent updateevent);
> All classes that are interested in configuration changes(batch changes not just one property
changes) can implement this class and register themselves in Configuration node in hierarchy.
> ------------------------------
> After some research! in Weblogic classes and jar files you can find the "com.bea.core.descriptor_1.4.0.0.jar"
in "BEA_HOME\modules" folder.
> After another research using Decompilers you can find some interesting classes like BeanUpdateListener,
BeanUpdateEvent, DescriptorBean, Descriptor inside "weblogic.descriptor" package. And also
another interesting class "weblogic.descriptor.internal.BeanDiff" class. Looking at the source
of them is useful!!
> I could not completely understand the model that Weblogic works but that point are what
I understood about it.
> I some useful features can be added to Apache Commons Config by looking at weblogic works.
It also can ease the process of writing ConfigurationMBeans for applications.
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